High Speed Photosensitive Devices and Associated Methods

ABSTRACT

High speed optoelectronic devices and associated methods are provided. In one aspect, for example, a high speed optoelectronic device can include a silicon material having an incident light surface, a first doped region and a second doped region forming a semiconductive junction in the silicon material, and a textured region coupled to the silicon material and positioned to interact with electromagnetic radiation. The optoelectronic device has a response time of from about 1 picosecond to about 5 nanoseconds and a responsivity of greater than or equal to about 0.4 A/W for electromagnetic radiation having at least one wavelength from about 800 nm to about 1200 nm.

PRIORITY DATA

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/356,536, filed on Jun. 18, 2010, which isincorporated herein by reference.

BACKGROUND

Many imaging applications such as hands-free gesture control, videogames, medical, and machine vision, as well as communicationapplications utilize various optoelectronic devices, such asphotodetectors and imaging arrays of photodetectors. Communicationapplications typically use, for example, fiber optical networks becausesuch networks perform well in the near infrared wavelengths of lightwhere optical fibers experience lower signal loss. Applications forlaser marking and range finding commonly use lasers with near infraredwavelengths such 1064 nm. Other applications such as depth perceptionapplications utilize imagers that can detect near infrared wavelengthssuch as 850 nm or 940 nm. These wavelengths are commonly generated fromlight emitting diodes or laser diodes made with gallium arsenide (GaAs).All of these applications require detectors or detector arrays with fastresponse time, typically faster than what can be achieved with a thick(eg >100 um) thick active layer of silicon. Therefore, the silicondevices utilized for these applications are often thin and have specificdesign considerations included to reduce response time. However, as theactive layer of silicon becomes thinner, the response at longerwavelengths (eg 850 nm, 940 nm, and 1064 nm) because much lower thanthat of a thick silicon device layer. Thick silicon devices with highresponse at longer wavelengths, on the other hand, have slow responsetime and are difficult to deplete.

SUMMARY

The present disclosure provides high speed optoelectronic devices andassociated methods. In one aspect, for example, a high speedoptoelectronic device can include a silicon material having an incidentlight surface, a first doped region and a second doped region forming asemiconductive junction in the silicon material, and a textured regioncoupled to the silicon material and positioned to interact withelectromagnetic radiation. The optoelectronic device has a response timeof from about 1 picosecond to about 5 nanoseconds and a responsivity ofgreater than or equal to about 0.4 A/W for electromagnetic radiationhaving at least one wavelength from about 800 nm to about 1200 nm. Inanother aspect, the optoelectronic device has a responsivity of greaterthan or equal to about 0.5 A/W for electromagnetic radiation having atleast one wavelength from about 800 nm to about 1200 nm. In yet anotheraspect, the optoelectronic device has a responsivity of greater than orequal to about 0.45 A/W for electromagnetic radiation having awavelength of about 850 nm. In a further aspect, the silicon materialhas a thickness of from about 1 μm to about 100 μm. In yet a furtheraspect, dark current of the device during operation is from about 100pA/cm² to about 10 nA/cm².

In another aspect, a high speed optoelectronic device can include asilicon material having an incident light surface, a first doped regionand a second doped region forming a semiconductive junction in thesilicon material, and a textured region coupled to the silicon materialand positioned to interact with electromagnetic radiation. Theoptoelectronic device has a response time of from about 1 picosecond toabout 5 nanoseconds and a responsivity of greater than or equal to about0.3 A/W for electromagnetic radiation having a wavelength of about 940nm.

In yet another aspect, high speed optoelectronic device can include asilicon material having an incident light surface, a first doped regionand a second doped region forming a semiconductive junction in thesilicon material, and a textured region coupled to the silicon materialand positioned to interact with electromagnetic radiation. Theoptoelectronic device has a response time of from about 1 picosecond toabout 5 nanoseconds and a responsivity of greater than or equal to about0.05 A/W for electromagnetic radiation having a wavelength of about 1060nm.

In another aspect, a photodiode array can include a silicon materialhaving an incident light surface, at least two photodiodes in thesilicon material, each photodiode including a first doped region and asecond doped region forming a junction, and a textured region coupled tothe silicon material and positioned to interact with electromagneticradiation. The photodiode array has a response time of from about 1picosecond to about 5 nanoseconds and a responsivity of greater than orequal to about 0.4 A/W for electromagnetic radiation having at least onewavelength from about 800 nm to about 1200 nm. In one aspect, thesilicon material has a thickness of from about 1 μm to about 100 μm.

In yet another aspect, a method of increasing the speed of anoptoelectronic device can include doping at least two regions in asilicon material to form at least one junction, and texturing thesilicon material to form a textured region positioned to interact withelectromagnetic radiation. The optoelectronic device has a response timeof from about 1 picosecond to about 5 nanoseconds and a responsivity ofgreater than or equal to about 0.4 A/W for electromagnetic radiationhaving at least one wavelength from about 800 nm to about 1200 nm. Inone aspect, the device can include a further doped region intended toquickly bring carriers from the side opposite junction to the junctionregion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation of the absorption characteristicsof a fast (or thin) photodetector device based on standard siliconcompared to the absorption characteristics of a photodetecting devicebased on silicon but having a textured region in accordance with oneaspect of the present disclosure;

FIG. 2 is a schematic view of a photosensitive device in accordance withanother aspect of the present disclosure;

FIG. 3 is a schematic view of a photosensitive device in accordance withyet another aspect of the present disclosure;

FIG. 4 is a schematic view of a photosensitive device in accordance witha further aspect of the present disclosure;

FIG. 5 is a schematic view of a photosensitive device in accordance withyet a further aspect of the present disclosure;

FIG. 6 is a schematic view of a photosensitive device in accordance withanother aspect of the present disclosure;

FIG. 7 is a schematic view of a photosensitive device in accordance withyet another aspect of the present disclosure;

FIG. 8 is a schematic view of a photosensitive array device inaccordance with a further aspect of the present disclosure;

FIG. 9 is an illustration of a time of flight measurement in accordancewith another aspect of the present disclosure;

FIG. 10 a is a schematic view of a pixel configuration for a photoimagerarray in accordance with another aspect of the present disclosure;

FIG. 10 b is a schematic view of a pixel configuration for a photoimagerarray in accordance with another aspect of the present disclosure;

FIG. 10 c is a schematic view of a pixel configuration for a photoimagerarray in accordance with another aspect of the present disclosure;

FIG. 11 is a schematic diagram of a six transistor imager in accordancewith another aspect of the present disclosure;

FIG. 12 is a schematic diagram of an eleven transistor imager inaccordance with another aspect of the present disclosure;

FIG. 13 is a schematic view of a photosensitive array device inaccordance with yet a further aspect of the present disclosure;

FIG. 14 is a schematic view of a photosensitive array device inaccordance with another aspect of the present disclosure; and

FIG. 15 is a depiction of a method of increasing the speed of anoptoelectronic device in accordance with yet another aspect of thepresent disclosure.

DETAILED DESCRIPTION

Before the present disclosure is described herein, it is to beunderstood that this disclosure is not limited to the particularstructures, process steps, or materials disclosed herein, but isextended to equivalents thereof as would be recognized by thoseordinarily skilled in the relevant arts. It should also be understoodthat terminology employed herein is used for the purpose of describingparticular embodiments only and is not intended to be limiting.

DEFINITIONS

The following terminology will be used in accordance with thedefinitions set forth below.

It should be noted that, as used in this specification and the appendedclaims, the singular forms “a,” and, “the” can include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to “a dopant” can include one or more of such dopants andreference to “the layer” can include reference to one or more of suchlayers.

As used herein, “quantum efficiency” (QE) is defined as the percentageof photons incident on an optoelectronic device that are converted intoelectrons. External QE (EQE) is defined as the current obtained outsideof the device per incoming photon. As such, EQE therefore depends onboth the absorption of photons and the collection of charges. The EQE islower than the QE due to recombination effects and optical losses (e.g.transmission and reflection losses).

As used herein, “responsivity” is a measure of the input-output gain ofa detector system. In the case of a photodetector, responsivity is ameasure of the electrical output per optical input. Responsivity of aphotodetector is expressed in amperes per watt of incident radiantpower. Additionally, responsivity is a function of the wavelength of theincident radiation and of the properties of the device, such as thebandgap of the material of which the device is made. One expression forresponsivity (R_(λ)) is shown in Equation I, where η is the externalquantum efficiency of the detector for a given wavelength (λ), q is thecharge of an electron, h is Planks constant, and ν is the frequency oflight.

$\begin{matrix}{R_{\lambda} = {{\frac{q}{hv} \times \eta} \approx {\frac{\lambda_{({\mu \; m})}}{1.23985} \times \eta}}} & (I)\end{matrix}$

As used herein, the terms “electromagnetic radiation” and “light” can beused interchangeably, and can represent wavelengths across a broadrange, including visible wavelengths (approximately 350 nm to 800 nm)and non-visible wavelengths (longer than about 800 nm or shorter than350 nm). The infrared spectrum is often described as including a nearinfrared portion of the spectrum including wavelengths of approximately800 to 1300 nm, a short wave infrared portion of the spectrum includingwavelengths of approximately 1300 nm to 3 micrometers, and a mid to longwave infrared (or thermal infrared) portion of the spectrum includingwavelengths greater than about 3 micrometers up to about 30 micrometers.These are generally and collectively referred to herein as “infrared”portions of the electromagnetic spectrum unless otherwise noted.

As used herein, “response time” refers to the rise time or fall time ofa detector device. In one aspect, “rise time” is the time differencebetween the 10% point and the 90% point of the peak amplitude output onthe leading edge of the electrical signal generated by the interactionof light with the device. “Fall time” is measured as the time differencebetween the 90% point and the 10% point of the trailing edge of theelectrical signal. In some aspects, fall time can be referred to as thedecay time.

As used herein, the terms “disordered surface” and “textured surface”can be used interchangeably, and refer to a surface having a topologywith nano- to micron-sized surface variations. Such a surface topologycan be formed by the irradiation of a laser pulse or laser pulses,chemical etching, lithographic patterning, interference of multiplesimultaneous laser pulses, or reactive ion etching. While thecharacteristics of such a surface can be variable depending on thematerials and techniques employed, in one aspect such a surface can beseveral hundred nanometers thick and made up of nanocrystallites (e.g.from about 10 to about 50 nanometers) and nanopores. In another aspect,such a surface can include micron-sized structures (e.g. about 1 μm toabout 60 μm). In yet another aspect, the surface can include nano-sizedand/or micron-sized structures from about 5 nm and about 500 μm.

As used herein, the term “fluence” refers to the amount of energy from asingle pulse of laser radiation that passes through a unit area. Inother words, “fluence” can be described as the energy density of onelaser pulse.

As used herein, the terms “surface modifying” and “surface modification”refer to the altering of a surface of a semiconductor material usinglaser irradiation, chemical etching, reactive ion etching, lithographicpatterning, etc. In one specific aspect, surface modification caninclude processes using primarily laser radiation or laser radiation incombination with a dopant, whereby the laser radiation facilitates theincorporation of the dopant into a surface of the semiconductormaterial. Accordingly, in one aspect surface modification includesdoping of a semiconductor material.

As used herein, the term “target region” refers to an area of asemiconductor material that is intended to be doped or surface modified.The target region of a semiconductor material can vary as the surfacemodifying process progresses. For example, after a first target regionis doped or surface modified, a second target region may be selected onthe same semiconductor material.

As used herein, the term “detection” refers to the sensing, absorption,and/or collection of electromagnetic radiation.

As used herein, the term “substantially” refers to the complete ornearly complete extent or degree of an action, characteristic, property,state, structure, item, or result. For example, an object that is“substantially” enclosed would mean that the object is either completelyenclosed or nearly completely enclosed. The exact allowable degree ofdeviation from absolute completeness may in some cases depend on thespecific context. However, generally speaking the nearness of completionwill be so as to have the same overall result as if absolute and totalcompletion were obtained. The use of “substantially” is equallyapplicable when used in a negative connotation to refer to the completeor near complete lack of an action, characteristic, property, state,structure, item, or result. For example, a composition that is“substantially free of” particles would either completely lackparticles, or so nearly completely lack particles that the effect wouldbe the same as if it completely lacked particles. In other words, acomposition that is “substantially free of” an ingredient or element maystill actually contain such item as long as there is no measurableeffect thereof.

As used herein, the term “about” is used to provide flexibility to anumerical range endpoint by providing that a given value may be “alittle above” or “a little below” the endpoint.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

Concentrations, amounts, and other numerical data may be expressed orpresented herein in a range format. It is to be understood that such arange format is used merely for convenience and brevity and thus shouldbe interpreted flexibly to include not only the numerical valuesexplicitly recited as the limits of the range, but also to include allthe individual numerical values or sub-ranges encompassed within thatrange as if each numerical value and sub-range is explicitly recited. Asan illustration, a numerical range of “about 1 to about 5” should beinterpreted to include not only the explicitly recited values of about 1to about 5, but also include individual values and sub-ranges within theindicated range. Thus, included in this numerical range are individualvalues such as 2, 3, and 4 and sub-ranges such as from 1-3, from 2-4,and from 3-5, etc., as well as 1, 2, 3, 4, and 5, individually.

This same principle applies to ranges reciting only one numerical valueas a minimum or a maximum. Furthermore, such an interpretation shouldapply regardless of the breadth of the range or the characteristicsbeing described.

The Disclosure

Many applications for optoelectronic devices can benefit from high speedoperation. For example, a photodetector used in applications such ascommunicating data, laser range finding, laser marking, time of flightimaging, and the like, can be a limiting factor in how fast data can betransmitted. Thus, a photodetector having a faster responsivity canreceive data at a correspondingly higher rate. The speed of manyoptoelectronic devices such as photodetectors is dependent, at least inpart, on the speed with which charge carriers are swept from thephotodetector. The speed at which carriers are swept from aphotodetector can depend on the distance a carrier has to travel,whether the carriers are generated in a region of the device with anelectric field, and the likelihood of a carrier being trapped or slowedin a defect within the device layer. In some cases, a bias can beapplied to the photodetector to decrease the response time by increasingthe drift velocity of the carriers. Additionally, many traditional datacommunication applications utilize electromagnetic radiation in the redand infrared spectrum as a data carrier. In a typical silicon device,electromagnetic radiation in the red and infrared spectrum generatecarriers deep into the silicon device, thus increasing the distance thecarrier has to travel to be collected. Thus it can be beneficial for aphotodetector to absorb infrared radiation in a thin device in order toincrease communication speeds and to reduce dark current.

Silicon is one material that can be used as a photodetectorsemiconductor. Thin silicon photodetectors are limited, however, intheir ability to detect infrared wavelengths, particularly whenfunctioning at higher data communication speeds. Traditional siliconmaterials require substantial absorption depths to detect photons havingwavelengths longer than about 700 nm. While visible light can beabsorbed at relatively shallow depths in silicon, absorption of longerwavelengths (e.g. 900 nm) in silicon of a thin wafer depth (e.g.approximately 100 μm) is poor if at all. Because short wave infraredlight is mostly transparent to silicon-based photodetectors, othermaterials (e.g. InGaAs) have traditionally been used to detect infraredelectromagnetic radiation having wavelengths greater than about 1100 nm.Using such other materials, however, is expensive, increases darkcurrent relative to silicon devices, and limits the detection ofelectromagnetic radiation in the visible spectrum (i.e. visible light,350 nm-800 nm). As such, silicon is often used because it is relativelycheap to manufacture and can be used to detect wavelengths in thevisible spectrum.

Accordingly, the present disclosure provides optoelectronic devices andassociated methods that increase the electromagnetic radiationabsorption range of thin silicon devices into the infrared region, thusallowing the absorption of visible and infrared light by such devices.Additionally, such devices can be configured to operate at much higherdata rates and have increased external quantum efficiencies andresponsivities as compared to traditional thin silicon devices operatingin the infrared spectrum. In one aspect, for example, a siliconphotodetector is provided that includes a textured region to increasethe absorption, external quantum efficiency, and to decrease responsetimes in the infrared wavelengths. Such unique and novel devices canoperate at high data rates in the visible and infrared spectrums. Suchan increased sensitivity in a silicon-based device can thus reduceprocessing cost of photodetectors, reduce the power needed in lightsources, increase the depth resolution in 3D types imaging, increase thedistance over which data can be transmitted, improve laser rangefinding, and increases opportunities to use longer wavelengths ofelectromagnetic radiation for communicating data.

In one aspect, for example, a high speed optoelectronic device isprovided. Such a device can include a silicon material having anincident light surface, a first doped region and a second doped regionforming a semiconductive junction in the silicon material, and atextured region coupled to the silicon material and positioned tointeract with electromagnetic radiation. The optoelectronic device has aresponse time of from about 1 picosecond to about 5 nanoseconds and aresponsivity of greater than or equal to about 0.4 A/W forelectromagnetic radiation having at least one wavelength from about 800nm to about 1200 nm. For example, FIG. 1 shows anabsorption/responsivity graph where the dashed line 12 represents theabsorption characteristics of a photodetector device based on standardfast silicon device and the solid line 14 represents the absorptioncharacteristics of a photodetecting device based on silicon but having atextured region. Notably, the absorption of a standard fast siliconphotodiode in the infrared, i.e. the 800 nm to 1200 nm region, resultsin relatively low responsivity.

Additionally, in one aspect the response time of the optoelectronicdevice is from about 1 picosecond to about 1 nanosecond. In anotheraspect, the response time of the optoelectronic device is from about 1picosecond to about 500 picoseconds.

In another aspect, the optoelectronic device has a responsivity ofgreater than or equal to about 0.5 A/W for electromagnetic radiationhaving at least one wavelength from about 800 nm to about 1200 nm. Inyet another aspect, the optoelectronic device has a responsivity ofgreater than or equal to about 0.45 A/W for electromagnetic radiationhaving a wavelength of about 850 nm. In a further aspect, theoptoelectronic device has a responsivity of greater than or equal toabout 0.3 A/W for electromagnetic radiation having a wavelength of about940 nm. In yet a further aspect, the optoelectronic device has aresponsivity of greater than or equal to about 0.05 A/W forelectromagnetic radiation having a wavelength of about 1060 nm.

In some aspects, the thickness of the device can dictate theresponsivity and response time. However standard silicon devices need tobe thick, i.e. greater than 100 μm in order to detect wavelengths in theinfrared spectrum, and such detection with thick devices results in aslow response and high dark current. It has now been discovered that atextured region positioned to interact with electromagnetic radiationcan increase the absorption of infrared light in a device, therebyimproving the infrared responsivity while allowing for fast operation.Diffuse scattering and reflection can result in increased path lengthsfor absorption, particularly if combined with total internal reflection,resulting in large improvements of responsivity in the infrared forsilicon photodiodes, photodetectors, photodiode arrays, and the like.Because of the increased path lengths for absorption, thinner siliconmaterials can be used to absorb electromagnetic radiation up into theinfrared regions. One advantage of thinner silicon material devices isthat charge carriers are more quickly swept from the device, thusdecreasing the response time. Conversely, thick silicon material devicessweep charge carriers therefrom more slowly, at least in part due todiffusion.

Thus, the devices of the present disclosure increase the absorption pathlength of silicon materials by increasing the absorption path length forlonger wavelengths as compared to traditional silicon devices. Theabsorption depth in silicon photodetectors is the depth into silicon atwhich the radiation intensity is reduced to about 36% of the value atthe surface of the silicon material. The increased absorption pathlength results in an apparent reduction in the absorption depth, or areduced apparent or effective absorption depth. For example, theeffective absorption depth of silicon can be reduced such that longerwavelengths can be absorbed at depths of less than or equal to about 100μm. By increasing the absorption path length, such devices are able toabsorb longer wavelengths (e.g. >1000 nm for silicon) within a thinsemiconductor material. In addition to decreasing the effectiveabsorption depth, the response time can be decreased using thinnersemiconductor materials.

Accordingly, optoelectronic devices according to aspects of the presentdisclosure provide, among other things, enhanced response in theinfrared light portion of the optical spectrum and improved response andquantum efficiency in converting electromagnetic radiation to electricalsignals. As such, high quantum efficiencies and high speeds can beobtained in the infrared for devices thinner than about 100 μm. In otherwords, the response is higher than that found in thicker devices atinfrared wavelengths.

In one aspect, as is shown in FIG. 2 for example, an optoelectronicdevice can include a silicon material 22 having a first doped region 24and a second doped region 26 associated therewith. The first and seconddoped regions thus form a semiconductive junction. Numerousconfigurations are contemplated, and any type of junction configurationis considered to be within the present scope. For example, the first andsecond doped regions can be distinct from one another, contacting oneanother, overlapping one another, etc. In some cases, an intrinsicregion can be located at least partially between the first and seconddoped regions.

The optoelectronic device can also include a textured region 28 coupledto the silicon material 22 and positioned to interact with incomingelectromagnetic radiation 29. In this case, the textured region islocated on a side of the silicon material that is opposite to the firstdoped region 24 and the second doped region 26. Electromagneticradiation that passes through the silicon material to contact thetextured region can be reflected back through the silicon material, thuseffectively increasing the absorption path length of the siliconmaterial. The textured region can be associated with an entire surfaceof the silicon material or only a portion thereof. Additionally, in someaspects the textured region can be specifically positioned to maximizethe absorption path length of the silicon material. In other aspects, athird doping can be included near the textured region to improve thecollection of carriers generated near the'textured region.

The silicon material can be of any thickness that allows electromagneticradiation detection and conversion functionality, and thus any suchthickness of silicon material is considered to be within the presentscope. Although any thickness of the silicon material is considered tobe within the present scope, thin silicon layer materials can beparticularly beneficial in decreasing the response time and/or thecapacitance of the device. As has been described, charge carriers can bemore quickly swept from thinner silicon material layers as compared tothicker silicon material layers. The thinner the silicon, the lessmaterial the electron/holes have to traverse in order to be collected,and the lower the probability of a generated charge carrier encounteringa defect that could trap or slow the collection of the carrier. Thus oneobjective to implementing a fast photo response is to utilize a thinsilicon material for the body region of the photodiode. Such a devicecan be nearly depleted of charge carriers by the built in potential ofthe photodiode and any applied bias to provide for a fast collection ofthe photo generated carriers by drift in an electric field. Chargecarriers remaining in any undepleted region of the photodiode arecollected by diffusion transport, which is slower than drift transport.For this reason, it is desirable to have the thickness of any regionwhere diffusion may dominate to be much thinner than the depleted driftregions. In silicon materials having the proper doping provides adepletion region of about 10 μm with no applied bias. As such, in someaspects it can be useful to utilize a silicon material layer having athickness less of less than about 100 μm, or less than about 10 μm. Inanother aspect, the silicon material can have a thickness and substratedoping concentration such that an applied bias generates an electricalfield sufficient for saturation velocity of the charge carriers. Itshould be noted that operating a photodiode, as disclosed herein, at azero bias can result in low noise but at a longer response time. Whenbias is applied however, the dark current is increased, resulting inhigher noise, but with a decreased response time. The increased darkcurrent can be compensated if the incident radiation signal is strong.The amount of dark current increase can be minimized, however, with athinner device layer.

Accordingly, in one aspect the silicon material has a thickness of fromabout 1 μm to about 100 μm. In another aspect, the silicon material hasa thickness of from about 1 μm to about 50 μm. In yet another aspect,the silicon material has a thickness of from about 5 μm to about 10 μm.In a further aspect, the silicon material has a thickness of from about1 μm to about 5 μm.

As has been described, the response time of an optoelectronic device islimited by the transit time of the photo generated carriers across thethickness of the substrate. The RC time constant of the load resistance,(R) and the capacitance (C) of the entire electronic device structurecan be kept less than this transit time value by using small loadresistors and keeping the capacitance of the photodiodes small bylimiting the doping density of the silicon material and area of thephotodiodes. For example, photodiodes doped at 10¹⁵/cm³ can have acapacitance that may be 10 nF/cm² without any applied bias. Small areaphotodiodes with 50 ohm load resistors can have very fast RC timeconstants. A photodiode with an area of 0.01 cm² can have a RC timeconstant of 0.5 nanoseconds. Given that the response time will belimited by the maximum charge carrier transit time across thephotodiode, then diffusion rates can place an upper limit on theresponse time for photodiodes of different thickness. For example, ifthe photodiodes have a thickness of less than d=100 μm, then thediffusion transit time can be calculated by Equation (II) below, where Dis the diffusion coefficient for electrons.

$\begin{matrix}\frac{d^{2}}{2D} & ({II})\end{matrix}$

The response time is bound by an upper limit of 2 μs. For light having awavelength of about 900 nm, only about 35% is absorbed in the first passor a device thinner than 100 μm and approximately 30% is reflected atthe first surface, thereby giving a responsivity on the order 10% or 0.1A/W. The responsivity, R, can be increased at least five fold by usingmultiple internal reflections to achieve a value of R=0.5 A/W.

In one aspect, a photodiode can have a thickness of less than about d=10μm. Using equation (I) above, the resultant upper response time limit isabout 20 ns. For light having a wavelength of about 700 nm with about33% absorbed in the first pass and about 30% being reflected at thefirst surface, the responsivity can be on the order 10% or 0.3Ampere/Watt. The responsivity, R, can be increased at least two fold byusing multiple internal reflections as described herein to achieve avalue of R=0.6 A/W.

In one aspect, for example, an optoelectronic device has a response timeof from about 100 picoseconds to about 1 nanosecond. In another aspect,an optoelectronic device has a responsivity of from about 0.4 A/W toabout 0.55 A/W for at least one wavelength of from about 800 nm to about1200 nm relative to standard silicon. In yet another aspect, anoptoelectronic device has a responsivity of from about 0.1 A/W to about0.55 A/W for at least one wavelength of from about 1000 nm to about 1200nm relative to standard silicon. In another aspect, the optoelectronicdevice has an increased external quantum efficiency of at least 10% forat least one wavelength of from about 550 nm to about 1200 nm relativeto a silicon device with comparable thickness and response time. In yetanother aspect, an optoelectronic device has a data rate greater than orequal to about 1 Gbs. In a further aspect, an optoelectronic device hasa data rate greater than or equal to about 2 Gbs.

As has been described, optoelectronic devices according to aspects ofthe present disclosure can exhibit lower levels of dark current ascompared to traditional devices. Although a variety of reasons arepossible, one exemplary reason may be that a thinner silicon materiallayer can have fewer crystalline defects responsible for the generationof dark current. In one aspect, for example, the dark current of anoptoelectronic device during operation is from about 100 pA/cm² to about10 nA/cm². In another aspect, the maximum dark current of anoptoelectronic device during operation is less than about 1 nA/cm².

Various types of silicon materials are contemplated, and any suchmaterial that can be incorporated into an optoelectronic device isconsidered to be within the present scope. In one aspect, for example,the silicon material is monocrystalline. In another aspect, the siliconmaterial is multicrystalline. In yet another aspect, the siliconmaterial is microcrystalline.

The silicon materials of the present disclosure can also be made using avariety of manufacturing processes. In some cases the manufacturingprocedures can affect the efficiency of the device, and may be takeninto account in achieving a desired result.

Exemplary manufacturing processes can include Czochralski (Cz)processes, magnetic Czochralski (mCz) processes, Float Zone (FZ)processes, epitaxial growth or deposition processes, and the like. Inone aspect, the silicon material is epitaxially grown.

As has been described, the textured region can function to diffuseelectromagnetic radiation, to redirect electromagnetic radiation, and toabsorb electromagnetic radiation, thus increasing the QE of the device.The textured region can include surface features to increase theeffective absorption length of the silicon material. The surfacefeatures can be cones, pyramids, pillars, protrusions, microlenses,quantum dots, inverted features and the like. Factors such asmanipulating the feature sizes, dimensions, material type, dopantprofiles, texture location, etc. can allow the diffusing region to betunable for a specific wavelength. In one aspect, tuning the device canallow specific wavelengths or ranges of wavelengths to be absorbed. Inanother aspect, tuning the device can allow specific wavelengths orranges of wavelengths to be reduced or eliminated via filtering.

As has been described, a textured region according to aspects of thepresent disclosure can allow a silicon material to experience multiplepasses of incident electromagnetic radiation within the device,particularly at longer wavelengths (i.e. infrared). Such internalreflection increases the effective absorption length to be greater thanthe thickness of the semiconductor substrate. This increase inabsorption length increases the quantum efficiency of the device,leading to an improved signal to noise ratio. The textured region can beassociated with the surface nearest the impinging electromagneticradiation, or the textured region can be associated with a surfaceopposite in relation to impinging electromagnetic radiation, therebyallowing the radiation to pass through the silicon material before ithits the textured region. Additionally, the textured region can bedoped. In one aspect, the textured region can be doped to the same orsimilar doping polarity as the silicon substrate so as to provide adoped contact region on the backside of the device.

The textured region can be formed by various techniques, includinglasing, chemical etching (e.g. anisotropic etching, isotropic etching),nanoimprinting, additional material deposition, reactive ion etching,and the like. One effective method of producing a textured region isthrough laser processing. Such laser processing allows discretelocations of the semiconductor substrate to be textured. A variety oftechniques of laser processing to form a textured region arecontemplated, and any technique capable of forming such a region shouldbe considered to be within the present scope. Laser treatment orprocessing can allow, among other things, enhanced absorption propertiesand thus increased electromagnetic radiation focusing and detection.

In one aspect, for example, a target region of the silicon material canbe irradiated with laser radiation to form a textured region. Examplesof such processing have been described in further detail in U.S. Pat.Nos. 7,057,256, 7,354,792 and 7,442,629, which are incorporated hereinby reference in their entireties. Briefly, a surface of a siliconmaterial is irradiated with laser radiation to form a textured orsurface modified region. Such laser processing can occur with or withouta dopant material. In those aspects whereby a dopant is used, the lasercan be directed through a dopant carrier and onto the silicon surface.In this way, dopant from the dopant carrier is introduced into thetarget region of the silicon material. Such a region incorporated into asilicon material can have various benefits in accordance with aspects ofthe present disclosure. For example, the target region typically has atextured surface that increases the surface area of the laser treatedregion and increases the probability of radiation absorption via themechanisms described herein. In one aspect, such a target region is asubstantially textured surface including micron-sized and/or nano-sizedsurface features that have been generated by the laser texturing. Inanother aspect, irradiating the surface of the silicon material includesexposing the laser radiation to a dopant such that irradiationincorporates the dopant into the semiconductor. Various dopant materialsare known in the art, and are discussed in more detail herein. It isalso understood that in some aspects such laser processing can occur inan environment that does not substantially dope the silicon material(e.g. an argon atmosphere).

Thus the surface of the silicon material that forms the textured regionis chemically and/or structurally altered by the laser treatment, whichmay, in some aspects, result in the formation of surface featuresappearing as nanostructures, microstructures, and/or patterned areas onthe surface and, if a dopant is used, the incorporation of such dopantsinto the semiconductor material. In some aspects, such features can beon the order of 50 nm to 20 μm in size and can assist in the absorptionof electromagnetic radiation. In other words, the textured surface canincrease the probability of incident radiation being absorbed by thesilicon material.

The type of laser radiation used to surface modify a silicon materialcan vary depending on the material and the intended modification. Anylaser radiation known in the art can be used with the devices andmethods of the present disclosure. There are a number of lasercharacteristics, however, that can affect the surface modificationprocess and/or the resulting product including, but not limited to thewavelength of the laser radiation, pulse width, pulse fluence, pulsefrequency, polarization, laser propagation direction relative to thesilicon material, etc. In one aspect, a laser can be configured toprovide pulsatile lasing of a silicon material. A short-pulsed laser isone capable of producing femtosecond, picosecond and/or nanosecond pulsedurations. Laser pulses can have a central wavelength in a range ofabout from about 10 nm to about 12 μm, and more specifically from about200 nm to about 1600 nm. The pulse width of the laser radiation can bein a range of from about tens of femtoseconds to about hundreds ofnanoseconds. In one aspect, laser pulse widths can be in the range offrom about 50 femtoseconds to about 50 picoseconds. In another aspect,laser pulse widths can be in the range of from about 50 picoseconds to100 nanoseconds. In another aspect, laser pulse widths are in the rangeof from about 50 to 500 femtoseconds.

The number of laser pulses irradiating a target region can be in a rangeof from about 1 to about 5000. In one aspect, the number of laser pulsesirradiating a target region can be from about 2 to about 1000. Further,the repetition rate or frequency of the pulses can be selected to be ina range of from about 10 Hz to about 10 MHz, or in a range of from about1 kHz to about 1 MHz, or in a range from about 10 Hz to about 10 kHz.Moreover, the fluence of each laser pulse can be in a range of fromabout 1 kJ/m² to about 20 kJ/m², or in a range of from about 3 kJ/m² toabout 8 kJ/m².

A variety of dopants are contemplated, and any such material that can beused in doping the first doped region, the second doped region, thetextured region, or any other doped portion of the optoelectronic deviceis considered to be within the present scope. It should be noted thatthe particular dopant utilized can vary depending on the siliconmaterial being laser treated, as well as the intended uses of theresulting silicon material.

A dopant can be either electron donating or hole donating. In oneaspect, non-limiting examples of dopants can include S, F, B, P, N, As,Se, Te, Ge, Ar, Ga, In, Sb, and combinations thereof. It should be notedthat the scope of dopants should include, not only the dopantsthemselves, but also materials in forms that deliver such dopants (i.e.dopant carriers). For example, S dopants includes not only S, but alsoany material capable being used to dope S into the target region, suchas, for example, H₂S, SF₆, SO₂, and the like, including combinationsthereof. In one specific aspect, the dopant can be S. Sulfur can bepresent at an ion dosage level of between about 5×10¹⁴ and about 1×10¹⁶ions/cm². Non-limiting examples of fluorine-containing compounds caninclude ClF₃, PF₅, F₂ SF₆, BF₃, GeF₄, WF₆, SiF₄, HF, CF₄, CHF₃, CH₂F₂,CH₃F, C₂F₆, C₂HF₅, C₃F₈, C₄F₈, NF₃, and the like, including combinationsthereof. Non-limiting examples of boron-containing compounds can includeB(CH₃)₃, BF₃, BCl₃, BN, C₂B₁₀H₁₂, borosilica, B₂H₆, and the like,including combinations thereof. Non-limiting examples ofphosphorous-containing compounds can include PF₅, PH₃, and the like,including combinations thereof. Non-limiting examples ofchlorine-containing compounds can include Cl₂, SiH₂Cl₂, HCl, SiCl₄, andthe like, including combinations thereof. Dopants can also includearsenic-containing compounds such as AsH₃ and the like, as well asantimony-containing compounds. Additionally, dopant materials caninclude mixtures or combinations across dopant groups, i.e. asulfur-containing compound mixed with a chlorine-containing compound. Inone aspect, the dopant material can have a density that is greater thanair. In one specific aspect, the dopant material can include Se, H₂S,SF₆, or mixtures thereof. In yet another specific aspect, the dopant canbe SF₆ and can have a predetermined concentration range of about5.0×10⁻⁸ mol/cm³ to about 5.0×10⁻⁴ mol/cm³. SF₆ gas is a good carrierfor the incorporation of sulfur into the semiconductor material via alaser process without significant adverse effects on the siliconmaterial. Additionally, it is noted that dopants can also be liquidsolutions of n-type or p-type dopant materials dissolved in a solutionsuch as water, alcohol, or an acid or basic solution. Dopants can alsobe solid materials applied as a powder or as a suspension dried onto thewafer.

Accordingly, the first doped region and the second doped region can bedoped with an electron donating or hole donating species to cause theregions to become more positive or negative in polarity as compared toeach other and/or the silicon substrate. In one aspect, for example,either doped region can be p-doped. In another aspect, either dopedregion can be n-doped. In one aspect, for example, the first dopedregion can be negative in polarity and the second doped region can bepositive in polarity by doping with p+ and n− dopants. In some aspects,variations of n(−−), n(−), n(+), n(++), p(−−), p(−), p(+), or p(++) typedoping of the regions can be used. Additionally, in some aspects thesilicon material can be doped in addition to the first and second dopedregions. The silicon material can be doped to have a doping polaritythat is different from one or more of the first and second dopedregions, of the silicon material can be doped to have a doping polaritythat is the same as one or more of the first and second doped regions.In one specific aspect, the silicon material can be doped to be p-typeand one or more of the first and second doped regions can be n-type. Inanother specific aspect, the silicon material can be doped to be n-typeand one or more of the first and second doped regions can be p-type. Inone aspect, at least one of the first or second doped regions has asurface area of from about 0.1 μm² to about 32 μm².

In another aspect, at least a portion of the textured region and/or thesilicon material can be doped with a dopant to generate a back surfacefield. A back surface field can function to repel generated chargecarriers from the backside of the device and toward the junction toimprove collection efficiency and speed. The addition of a back surfacefield can increase charge carrier collection and depletion. The presenceof a back surface field also acts to suppress dark current contributionfrom the surface of a device.

In another aspect, as is shown in FIG. 3, an optoelectronic device caninclude a silicon material 32 having a first doped region 34 and asecond doped region 36 associated therewith, where the first and seconddoped regions form a semiconductive photodiode junction. A texturedregion 38 is coupled to the silicon material, and is positioned tointeract with electromagnetic radiation. The optoelectronic device canalso include a first contact 37 to provide electrical contact to oneside of the device, and a second contact 39 to provide electricalcontact with the other side of the device. In one aspect, the firstcontact and the second contact are opposite in voltage polarity from oneanother. Note that in some aspects, the first and second contacts can beon the same side of the device (not shown). Additionally, a supportsubstrate 35 can be coupled to the device in order to provide structuralstability thereto. In one aspect, the one of the contacts can be a dopedportion of the textured region. Either a portion of the textured regionor the entire textured region can be doped to create one of thecontacts.

While the optoelectronic devices according to aspects of the presentdisclosure can operate in the absence of a bias at high speeds, in oneaspect a reverse bias is applied across the first and second contacts.Such a reverse bias can function to decrease the response time of thedevice by more quickly sweeping charge carriers from the siliconmaterial. Accordingly, for those situations whereby a bias is used, anybias voltage capable of sweeping charge carriers from the siliconmaterial is considered to be within the present scope. In one aspect,for example, the reverse bias is from about 0.001 V to about 20 V. Inanother aspect, the reverse bias is from about 0.001 V to about 10 V. Inyet another aspect, the reverse bias is from about 0.001 V to about 5 V.In a further aspect, the reverse bias is from about 0.001 V to about 3V. In yet a further aspect, the reverse bias is from about 3 V to about5 V. In some aspects, the reverse bias can be absent, or in other words,0 V is applied across the first and second contacts. In such cases, thecharge carriers can be depleted from the silicon material by thejunction potential created by the first and second doped regions.

In some aspects, the first and second doped regions can be on oppositesides of the silicon material. As is shown in FIG. 4, for example, asilicon material 42 can include a first doped region 44 associated withone surface of the silicon material and a second doped region 46associated with the opposite side of the silicon material. Furthermore,the textured region can be associated with either doped region. As isshown in FIG. 5, for example, a silicon material 52 can include a firstdoped region 54 associated with one surface of the silicon material anda second doped region 56 associated with the opposite side of thesilicon material, where a textured region 58 is associated with thefirst doped region. In another aspect, the textured region is associatedwith the second doped region (not shown). In a further aspect, atextured region can be associated with each doped region (not shown).

In another aspect, as is shown in FIG. 6, a silicon material 62 can havea first doped region 64 and a second dope region 66 on one surface, anda textured region 68 on an opposing surface. In this case,electromagnetic radiation 69 is incident on the side of the siliconmaterial having the textured surface. In another aspect, as is shown inFIG. 7, a silicon material 72 can have a first doped region 74 and asecond doped region 76 on an opposing surface to a textured region 78.An antireflective layer 77 can be coupled to the silicon material on theopposite surface to the textured layer. In some aspects, theantireflective layer can be on the same side of the silicon material asthe textured region (not shown). Furthermore, in some aspects a lens canbe optically coupled to the silicon material and positioned to focusincident electromagnetic radiation into the silicon material.

In another aspect of the present disclosure, a photodiode array isprovided. Such an array can include a silicon material having anincident light surface, at least two photodiodes in the siliconmaterial, where each photodiode includes a first doped region and asecond doped region forming a junction, and a textured region coupled tothe silicon material and positioned to interact with electromagneticradiation. The textured region can be a single textured region ormultiple textured regions. Additionally, the photodiode array has aresponse time of from about 1 picosecond to about 5 nanoseconds and aresponsivity of greater than or equal to about 0.4 A/W forelectromagnetic radiation having at least one wavelength from about 800nm to about 1200 nm.

As is shown in FIG. 8, for example, a silicon material 88 can include atleast two photodiodes 83 each having a first doped region 84 and asecond doped region 86. A textured region 88 is positioned to interactwith electromagnetic radiation. FIG. 8 shows a separate textured regionfor each photodiode. In some aspects, a single textured region can beused to increase the absorption path lengths of multiple photodiodes inthe array. Furthermore, an isolation structure 57 can be positionedbetween the photodiodes to electrically and/or optically isolate thephotodiodes from one another. In another aspect, the photodiode arraycan be electronically coupled to electronic circuitry to process thesignals generated by each photodiode.

Various types of isolation structures are contemplated, and any suchisolation is considered to be within the present scope. The isolationstructure can be shallow or deep trench isolation. Furthermore, theisolation structure can include depths between traditional shallow anddeep isolation, depending on the device design. Isolation structures caninclude dielectric materials, reflective materials, conductivematerials, and combinations thereof, including textured regions andother light diffusing features. Thus the isolation structure can beconfigured to reflect incident electromagnetic radiation, in some casesuntil it is absorbed, thereby increasing the effective absorption lengthof the device.

Photodiode arrays can have a variety of uses. For example, in one aspectsuch an array can be an imager. Numerous types of imagers arecontemplated, and any such imager or imaging application is consideredto be within the present scope. Non-limiting examples include 3Dimaging, machine vision, night vision, security and surveillance,various commercial applications, laser range finding and marking, andthe like. Thus, in the case of 3D imaging for example, the array isoperable to detect a phase delay between a reflected and an emittedoptical signal. As one example, various applications can benefit fromdepth information, such as hands-free gesture control, video games,medical applications, machine vision, etc. Time-of-flight (TOF) is atechnique developed for use in radar and LIDAR (Light Detection andRanging) systems to provide depth information. The basic principle ofTOF involves sending a signal and measuring a property of the returnedsignal from a target. The measured property is used to determine theTOF. Distance to the target is therefore derived by multiplication ofhalf the TOF and the velocity of the signal.

FIG. 9 illustrates a time of flight measurement with a target havingmultiple surfaces that are separated spatially. Equation (III) can beused to measure the distance to a target where d is the distance to thetarget and c is the speed of light.

$\begin{matrix}{d = \frac{{TOF}*c}{2}} & ({III})\end{matrix}$

By measuring the time (e.g. TOF) it takes for light to be emitted from alight source 92, travel to and from a target 94, the distance betweenthe light source (e.g. a light emitting diode (LED)) and the surface ofthe target can be derived. For an imager, if each pixel can perform theabove TOF measurement, a 3D image of the target can be achieved. Thedistance measurements become difficult with TOF methods when the targetis relatively near the source due to the high speed of light. In oneaspect, therefore, a TOF measurement can utilize a modulated LED lightpulse and measure the phase delay between emitted light and receivedlight. Based on the phase delay and the LED pulse width, the TOF can bederived.

TOF concept has been utilized in both CMOS and CCD sensor to obtaindepth information from each pixel. In many traditional 3D TOF sensors,an infrared LED or laser emits a modulated light pulse to illuminate atarget. The measured phase shift between emitted and received light canbe used to derive the depth information. Such methods, however, can havevarious problematic issues. For example, ambiguity (e.g. aliasing)occurs if the TOF difference between two targets is equal to half periodof light source modulation frequency. To solve the ambiguity issue, anoften used approach is to measure the same scene with multiplemodulation frequencies. In addition, due to the use of near infrared LEDor laser, a good color image normally cannot be achieved by the same 3DTOF sensor since an infrared (IR) cut filter cannot be used. Further,many current 3D TOF sensors operate in a rolling shutter mode. Inrolling shutter mode an image is captured by scanning across the frameeither vertically or horizontally. Motion artifacts are known toaccompany cameras that use the rolling shutter mode and can severelydegrade the quality of the depth map. Another issue occurs when ambientlight creates an un-wanted offset in the signal output. The photon-shotnoise related to the signal offset will degrade the signal-to-noise(SNR) ratio of the useful signal related to modulated near infrared(NIR) light emitting diode (LED). Therefore, many current 3D TOF imagerscannot operate outdoors (e.g. bright ambient light). In addition to theambient light, any dark current will also contribute to the un-wantedoffset, which is same as normal visible pixel.

As one example, a 3D pixel, such as a TOF 3D pixel with enhancedinfrared response can improve depth accuracy. In one aspect, aphotoimager array can include at least one 3D infrared detecting pixeland at least one visible light detecting pixel arranged monolithicallyin relation to each other. FIGS. 10 a-c show non-limiting exampleconfigurations of pixel arrangements of such arrays. FIG. 10 a shows oneexample of a pixel array arrangement having a red pixel 102, a bluepixel 104, and a green pixel 106. Additionally, two 3D TOF pixels (108and 109) having enhanced responsivity or detectability in the infraredregions of the light spectrum are included. The combination of two 3Dpixels allows for better depth perception. In FIG. 10 b, the pixelarrangement shown includes an imager as described in FIG. 10 a and threearrays of a red pixel, a blue pixel, and two green pixels. Essentially,one TOF pixel (108 and 109) replaces one quadrant of a RGGB pixeldesign. In this configuration, the addition of several green pixelsallows for the capture of more green wavelengths that is needed forgreen color sensitivity need for the human eye, while at the same timecapturing the infrared light for depth perception. It should be notedthat the present scope should not be limited by the number orarrangements of pixel arrays, and that any number and/or arrangement isincluded in the present scope. FIG. 10 c shows another arrangement ofpixels according to yet another aspect.

Various imager configurations and components are contemplated, and anysuch should be considered to be within the present scope. Non-limitingexamples of such components can include a carrier wafer, anantireflective layer, a dielectric layer, circuitry layer, a via(s), atransfer gate, an infrared filter, a color filter array (CFA), aninfrared cut filter, an isolation feature, and the like. Additionally,such devices can have light absorbing properties and elements as hasbeen disclosed in U.S. patent application Ser. No. 12/885,158, filed onSep. 17, 2010 which is incorporated by reference in its entirety.

As has been described, a TOF pixel can have an on-pixel optical narrowband pass filter. The narrow band pass filter design can match themodulated light source (either LED or laser) emission spectrum and maysignificantly reduce unwanted ambient light that can further increasethe signal to noise ratio of modulated infrared light. Another benefitof increased infrared QE is the possibility of high frame rate operationfor high speed 3D image capture. An integrated infrared cut filter canallow a high quality visible image with high fidelity color rendering.Integrating an infrared cut filter onto the sensor chip can also reducethe total system cost of a camera module (due to the removal of typicalIR filter glass) and reduce module profile (good for mobileapplications).

The thickness and responsivity of a QE enhanced imager can havesignificant impact on a TOF pixel operation, due to the increased speedand detection. The increased QE will contribute to higher image signalto noise, which will greatly reduce depth error. Further, increased QEon a silicon material having a thickness of less than about 100 μm canallow the pixel to reduce the diffusion component of signal so that thecharge collection and transfer speed can be increased, which is good forTOF pixel operation. In general, the photo-generated carrier createdinside pixel will depend on two mechanisms for collection: drift anddiffusion. For light having shorter wavelengths, most of the chargecarriers will be generated in a shallow region of the device and withinthe depletion region of the diode. Those carriers can be collectedrelatively fast, via drift. For infrared light, the majority of photocarriers are be generated deeper inside the silicon material. To achievehigher QE, normally thick silicon layers are used. As such, most of thecharge carriers carrier will be generated outside the diode's depletionregion and will depend on diffusion to be collected. For a 3D TOF pixel,however, a fast sampling of photo generated charge is beneficial.

For the devices according to aspects, of the present disclosure, a highQE can be achieved within a thin (i.e. less than 100 μm) layer ofsilicon material. Therefore, substantially all of the carriers generatedcan be collected via drift mechanism. This allows a fast chargecollection and transfer.

FIG. 11 shows an exemplary schematic for a six-transistor (6-T)architecture which will allow global shutter operation according to oneaspect of the present disclosure. The pixel can include a photodiode(PD), a global reset (Global_RST), a global transfer gate (Global_TX), astorage node, a transfer gate (TX1), reset (RST), source follower (SF),floating diffusion (FD), row select transistor (RS), power supply(Vaapix) and voltage out (Vout). Due to the use of extra transfer gateand storage node, correlated-double-sampling (CDS) is allowed.Therefore, the read noise should be able to match typical CMOS 4Tpixels.

FIG. 12 shows an exemplary schematic of a 3D TOF pixel according to oneaspect of the present disclosure. The 3D TOF pixel can have 11transistors for accomplishing the depth measurement of the target. Inthis embodiment the 3D pixel can comprise a photodiode (PD), a globalreset (Global_RST), a first global transfer gate (Global_TX1), a firststorage node, a first transfer gate (TX1), a first reset (RST1), a firstsource follower (SF1), a first floating diffusion (FD1), a first rowselect transistor (RS1), a second global transfer gate (Global_TX2), asecond storage node, a second transfer gate (TX2), a second reset(RST2), a second source follower (SF2), a second floating diffusion(FD2), a second row select transistor (RS2), power supply (Vaapix) andvoltage out (Vout). Other transistors can be included in the 3Darchitecture and should be considered within the scope of the presentinvention. The specific embodiment with 11 transistors can reduce motionartifacts due to the global shutter operation, thereby giving moreaccurate measurements.

As has been described, a photodiode array can be used in variouscommunication applications. For example, the array can be used to detectpulsed optical signals. Such pulsed signals can be used to carry data athigh speeds. By utilizing photodiodes having fast response times, veryshort pulse widths can be detected, thus increasing the speed of datacommunication. In one aspect, for example, the pulsed optical signalscan have pulse widths from about 1 femtosecond to about 1 microsecond.In another aspect, the at least two photodiodes are operable to transmitdata at a rate of at least 1 Gbps. In yet another aspect, the at leasttwo photodiodes are operable to transmit data at a rate of at least 2Gbps.

In one aspect, an array of four photodiodes forming a quad photodiodearray (quad array) is provided. A quad array can be used in a variety ofapplications, including communications, laser range finding, laseralignment, and the like. In some aspects, the four photodiodes can haveuniform photo response, or in other words, are selective to the samewavelength range. It can also be beneficial to have little to noelectrical and/or optical cross talk between the photodiodes in the quadarray. For this reason, isolation structures can be disposed between thephotodiodes can be beneficial. Some application can also benefit fromthe high speed operation of the photodiodes according to aspects of thepresent disclosure. FIGS. 13 and 14 show exemplary configurations ofquad arrays. FIG. 13 shows a quad array of four photodiodes 130including a silicon material 132 and a doped region 134. The dopedregion is made up of multiple doped regions forming a junction. Anisolation structure 136 is located between the photodiodes toelectrically and/or optically isolate the photodiodes againstundesirable cross talk. FIG. 14 shows a similar arrangement in acircular configuration. This array includes four photodiodes 140including a silicon material 142, a doped region 144, and an isolationstructure 146. In addition to those materials discussed herein, theisolation structure can include a dielectric material for electricalisolation and a metal material for a high reflectivity to the lightincidence on the walls of the trench. In one aspect, the sides andsurfaces of the diode between the isolation regions can be more heavilydoped than the silicon material in order to pin the Fermi level at theband edge and reduce the dark current. The photodiode can also include aburied layer of opposite conductivity type to the silicon material. Insome aspects, the doping of the silicon material can be kept low and thethickness can be thinned to provide a fast response time to the opticalsignal. A textured region can function to backside scatter light thatpasses through the silicon material, thus improving near infraredresponsivity.

In yet another aspect, a method of increasing the speed of anoptoelectronic device is provided. As is shown in FIG. 15, such a methodcan include doping at least two regions in a silicon material to form atleast one junction 152 and texturing the silicon material to form atextured region positioned to interact with electromagnetic radiation154. The optoelectronic device has a response time of from about 1picosecond to about 5 nanoseconds and a responsivity of greater than orequal to about 0.4 A/W for electromagnetic radiation having at least onewavelength from about 800 nm to about 1200 nm.

Of course, it is to be understood that the above-described arrangementsare only illustrative of the application of the principles of thepresent invention. Numerous modifications and alternative arrangementsmay be devised by those skilled in the art without departing from thespirit and scope of the present invention and the appended claims areintended to cover such modifications and arrangements. Thus, while thepresent invention has been described above with particularity and detailin connection with what is presently deemed to be the most practical andpreferred embodiments of the invention, it will be apparent to those ofordinary skill in the art that numerous modifications, including, butnot limited to, variations in size, materials, shape, form, function andmanner of operation, assembly and use may be made without departing fromthe principles and concepts set forth herein.

1. A high speed optoelectronic device, comprising: a silicon materialhaving an incident light surface; a first doped region and a seconddoped region forming a semiconductive junction in the silicon material;and a textured region coupled to the silicon material and positioned tointeract with electromagnetic radiation; wherein the optoelectronicdevice has a response time of from about 1 picosecond to about 5nanoseconds and a responsivity of greater than or equal to about 0.4 A/Wfor electromagnetic radiation having at least one wavelength from about800 nm to about 1200 nm.
 2. The device of claim 1, wherein the siliconmaterial has a thickness of from about 1 μm to about 100 μm.
 3. Thedevice of claim 1, wherein the optoelectronic device has a responsivityof greater than or equal to about 0.5 A/W for electromagnetic radiationhaving at least one wavelength from about 800 nm to about 1200 nm. 4.The device of claim 1, wherein the optoelectronic device has aresponsivity of greater than or equal to about 0.45 A/W forelectromagnetic radiation having a wavelength of about 850 nm.
 5. Thedevice of claim 1, wherein the optoelectronic device has a response timeof from about 1 picosecond to about 1 nanosecond.
 6. The device of claim1, wherein the first doped region has a surface area of from about 0.1μm² to about 32 μm².
 7. The device of claim 1, wherein theoptoelectronic device has a data rate greater than or equal to about 1Gbs.
 8. The device of claim 1, further comprising a first contact and asecond contact, wherein the first contact is opposite in voltagepolarity from the second contact.
 9. The device of claim 8, wherein areverse bias is applied across the first and second contacts.
 10. Thedevice of claim 9, wherein the reverse bias is from about 0.001 V toabout 20 V.
 11. The device of claim 8, wherein a bias is not appliedacross the first and second contacts during use.
 12. The device of claim1, wherein dark current of the device during operation is from about 100pA/cm² to about 10 nA/cm².
 13. The device of claim 1, wherein maximumdark current of the device during operation is less than about 1 nA/cm².14. The device of claim 1, wherein the textured region is positioned onan opposite side of the silicon material from the incident lightsurface.
 15. A high speed optoelectronic device, comprising: a siliconmaterial having an incident light surface; a first doped region and asecond doped region forming a semiconductive junction in the siliconmaterial; and a textured region coupled to the silicon material andpositioned to interact with electromagnetic radiation; wherein theoptoelectronic device has a response time of from about 1 picosecond toabout 5 nanoseconds and a responsivity of greater than or equal to about0.3 A/W for electromagnetic radiation having a wavelength of about 940nm.
 16. A high speed optoelectronic device, comprising: a siliconmaterial having an incident light surface; a first doped region and asecond doped region forming a semiconductive junction in the siliconmaterial; and a textured region coupled to the silicon material andpositioned to interact with electromagnetic radiation; wherein theoptoelectronic device has a response time of from about 1 picosecond toabout 5 nanoseconds and a responsivity of greater than or equal to about0.05 A/W for electromagnetic radiation having a wavelength of about 1060nm.
 17. A photodiode array, comprising a silicon material having anincident light surface; at least two photodiodes in the siliconmaterial, each photodiode including a first doped region and a seconddoped region forming a junction; and a textured region coupled to thesilicon material and positioned to interact with electromagneticradiation; wherein the photodiode array has a response time of fromabout 1 picosecond to about 5 nanoseconds and a responsivity of greaterthan or equal to about 0.4 A/W for electromagnetic radiation having atleast one wavelength from about 800 nm to about 1200 nm.
 18. The arrayof claim '7, wherein the silicon material has a thickness of from about1 μm to about 100 μm.
 19. The array of claim '7, wherein the at leasttwo photodiodes are four photodiodes forming a quad array.
 20. The arrayof claim '9, wherein the four photodiodes of the quad array areselective to a single wavelength range.
 21. The array of claim 17,wherein the array is an image sensor.
 22. The array of claim 17, whereinthe array is operable to detect a phase delay between a reflected and anemitted optical signal.
 23. The array of claim 17, wherein the array isoperable to detect pulsed optical signals.
 24. The array of claim 17,wherein the at least two photodiodes are operable to transmit data at arate of at least 1 Gbps.
 25. A method of increasing the speed of anoptoelectronic device, comprising: doping at least two regions in asilicon material to form at least one junction; and texturing thesilicon material to form a textured region positioned to interact withelectromagnetic radiation; wherein the optoelectronic device has aresponse time of from about 1 picosecond to about 5 nanoseconds and aresponsivity of greater than or equal to about 0.4 A/W forelectromagnetic radiation having at least one wavelength from about 800nm to about 1200 nm.